I don't think they have to match exactly, but it is nice to have the same shades perhaps. Whether they are the same height depends on where they are in the room. For instance, I don't think end tables flaning a sofa should have two differnt height lamps, but an easy chair in the same room could have a different height.

You can definitely mix styles and heights of lamps, but they need to complement each other in style, color, shades, or some other aspect. They shouldn't just be random different lamps.

Thanks for your input! I was at least thinking in the right direction.

Put concealed lights in the ceiling, yet they should be placed to provide bright spots according to furniture layout. Secondly place some pedestal lamps in the corners for comfortable reading if required. Lights should be bright but subtle